"A cornerstone of both of our drug testing programs has always been that you are responsible for what is in your body," Greg Aiello, NFL senior vice president of communications, said via email Tuesday. "It is stated that way in the policies."

In addition, several other players have been suspended for "not being responsible for what is in your body," as Aiello described.

Gordon himself is one example. A year ago, he said he tested positive for codeine in his prescribed cough medicine. Codeine is a banned substance, and he was suspended because he was responsible for knowing what he was taking. The four-game suspension was negotiated to a two-game ban and four games without pay.

Indianapolis Colts defensive end Robert Mathis was suspended four games for using what he said was a fertility drug banned by the NFL because it increases testosterone levels.

Adolpho Birch, the NFL vice president of labor policy and government affairs, has said often that players can reach out to the league before taking any drug to ensure it does not contain a banned substance. Once a positive test comes back for substance-abuse drugs, the league follows rules agreed to in the collective bargaining agreement.